1. Field of the Invention
The present invention relates to a guide unit performing guidance of relative motion that is used in mechanisms that perform relative motion in, for example, machine tools and industrial robots, and a direct drive unit to which a driving device in the form of a direct current linear motor is added to said guide unit.
2. Description of the Prior Art
An example of this type of guide unit and direct drive unit of the prior art is indicated in FIG. 1.
As indicated in FIG. 1, said guide unit has long track rail 1 and slider 2 that moves along said track rail 1. More specifically, four rollers (not shown) are mounted on slider 2, and these rollers roll on a track formed along the lengthwise direction of track rail 1.
Protruding portion la is formed on one side of track rail 1. A detected element in the form of linear scale 4 is provided on said protruding portion la roughly over its entire length. In contrast, small bracket 2a is provided on the side of slider 2, and detecting elements in the form of light emitting element 5a and light receiving element 5b are mounted on said small bracket 2a. A position detection device for detecting the position of slider 2 with respect to track rail 1 is thus composed of linear scale 4, light emitting element 5a and light receiving element 5b.
On the other hand, the direct current linear motor that composes the above-mentioned guide unit along with a direct drive unit is composed as described below.
As indicated in the drawing, said linear motor is composed of a primary side, equipped with a plurality of armature coils 7 arranged side by side in the lengthwise direction of track rail 1 on said track rail 1, and a secondary side having a field magnet (not shown) attached to the bottom surface of slider 2. Furthermore, each armature coil 7 is respectively wrapped in the form of, for example, a rectangular loop. In addition, said field magnet contains a plurality of N and S magnetic poles alternately arranged along the direction in which slider 2 is to move, or in other words, along the lengthwise direction of track rail 1. Furthermore, slider 2 has high magnetic permeability, and acts as magnet yoke that composes the above-mentioned secondary side together with said field magnet.
In the direct drive unit having the constitution described above, thrust is generated in accordance with Fleming's left hand rule between the primary side and secondary side as a result of a prescribed electric current being supplied to armature coils 7. For example, if track rail 1 coupled to the primary side is taken to be the stationary side, slider 2, integrated into a single unit with the secondary side, moves as a result of this thrust. The position of slide 2 with respect to track rail 1 is then detected by the above-mentioned position detection device.
The examples of a guide unit and direct drive unit of the prior art described above have the shortcoming of each of the components that compose the position detection device for detecting the relative positions of track rail 1 and slider 2 occupying a relatively large amount of space, making this a problem to be solved in terms of achieving reduced size of the overall units.